Welcome aboard, Ray!
I know what you mean about trying a camera more up to date - the 645 is a very different feel, bigger and heavier, but with automation and convenience... not to mention you hold it to your eye instead of your belly
I can say I've carried a TLR around more than the 645, due to the weight thing, but one of these days I'll build up the courage to take my 645 for a day's jaunt.